Abstract Apparatus and method for automatically injecting and/or withdrawing air from tubularly extruded film when needed, to obtain precise size control of the film. Such apparatus can include movable, opposed follower assemblies gravity operated inwardly toward the film to continuously engage opposite sides thereof, respectively, while still in the inflated condition. Any relative movement between the followers indicates a film size change, and is converted into electrical signals such as by potentiometer means or the like. Such signals energize electronic circuitry which, in turn, operates electrical valving means for inserting or withdrawing air from the film at the proper moment. The apparatus is not affected by film edge wrinkle or lateral sway of the film during measurement and, in addition, does not require drive motors or the like to operate.
Apparatus for controlling the size of tubular extruded film, and operative at a region in the manufacture of the film where the film is inflated and moving forward, said apparatus comprising conforming means to engage opposite sides of the film to partially collapse the film, oppositely disposed areas of the film being bulged outwardly in configuration by the pressure of the collapsing means, a pair of oppositely disposed independently movable film followers, means to gravity operate said followers to urge the same inwardly toward said film to resiliently ride against and follow any lateral movement of said bulged areas, respectively, whereby relative movement between said followers automatically indicates film size changes, and means for controlling the size of said film responsive to the relative movement of said followers.
Claim 2
Dependent Claim
128 words
Apparatus for controlling the size of tubular extruded film, and operative at a region in the manufacture of the film where the film is inflated and moving forward, said apparatus comprising conforming means to engage opposite sides of the film to partially collapse the film, oppositely disposed areas of the film being bulged outwardly in configuration by the pressure of the collapsing means, a pair of oppositely disposed independently movable film followers, means to gravity operate said followers to urge the same inwardly toward said film to resiliently ride against and follow any lateral movement of said bulged areas, respectively, whereby relative movement between said followers automatically indicates film size changes, and means for controlling the size of said film responsive to the relative movement of said followers.
Claim 3
Dependent Claim
33 words
The apparatus of claim 1 wherein said followers comprise opposed members freely swingable toward and away from each other, and gravity operated inwardly to movingly engage said bulged areas, respectively, of the film.
Claim 4
Dependent Claim
32 words
The apparatus of claim 1 wherein said followers are freely movable toward and away from each other, and are counter-weighted inwardly such as to be resiliently urged against said bulged areas, respectively.
Claim 5
Dependent Claim
13 words
The apparatus of claim 1 wherein said conforming means comprises a collapsing rack.